(1) Field of the Invention
The invention generally relates to means and methods of testing the strength of rigid materials such as concrete. More particularly, the invention relates to the placement of testing equipment within voids of the tested material.
(2) Description of the Related Art
Testing of concrete is known in the related art, as concrete and similar materials have been and continue to be widely used. An excellent prior art example is U.S. Pat. No. 3,283,566 issued on Nov. 8, 1966 to the inventor of the present invention, Dale Howard Fietz. The '566 patent entitled “Material Hardness Tester” discloses a strain gauge placed within a void and an assembly of mechanical components driving by an external torque wrench. Friction and other variables needed to be calculated in order to determine material hardness.
U.S. Pat. No. 3,640,126 issued on Feb. 8, 1972 to Moshe Te'eni discloses a system of using a void with a large base and narrow neck. An apparatus is placed in the void, expanded to fill the large base section and then withdrawn until concrete is dislodged. The Te'eni method required the drilling of a non-uniform cylinder and the use of complex mechanical components subject to many frictional forces. Te'eni would occasionally result in material being pulled out during testing, destroying the surrounding material and preventing any possibility of repeating a test in the same location.
U.S. Pat. No. 4,748,855 issued on Jun. 7, 1998 to Barnoff presents a complex system comprising a force rod and bearing shoes fitted into a cylindrical housing. The housing is lowered into a void or cylinder of concrete. The force rod comprises various cam structures subject to frictional forces and material hardness is derived by the measurement of torque to the force rod. Frictional forces from the cam section of the force rod and bearing shoe linkage needed to be calculated and such frictional forces directly compromised the integrity of the test results. Thus, there is a need in the art for improved means and methods of using existing cylinders, core holes or voids to measure material properties.